US Secretary of State John Kerry, who is on a tour of Asia, wants to seek more support from China in the denuclearization of the Korean Peninsula.

Issues such as the denuclearization and climate change are high on the agenda during Kerry's trip to China on Friday and Saturday while he will also raise concerns about the tensions in the East and South China Seas, according to senior State Department officials in a background briefing on Thursday for Kerry's trip.

In Seoul on Thursday, Kerry said the US will not accept the Democratic People's Republic of Korea as a nuclear armed state. "We will not accept talks for the sake of talks. And the DPRK must show that it will negotiate and live up to its commitments regarding denuclearization," Kerry said in a joint press conference with South Korean Foreign Minister Yun Byung-se.

The DPRK has expressed its willingness to come back to the Six-Party Talks on the denuclearization of the Korean Peninsula but without precondition. The US has insisted that DPRK must first honor its previous commitment on denuclearization. The Six-Party Talks, which have been stalled since 2008, involve the two Koreas, China, the US, Russia and Japan.

"We are committed to going to talks only if there is a clarity with respect to the steps that need to be taken for denuclearization by the North," Kerry said.

Kerry was in Beijing last April to seek Chinese help when tensions over the Korean Peninsula reached a boiling point. Following the DPRK's third nuclear test in February last year, the US sent bombers and aircraft carrier to demonstrate its force. The DPRK threatened an all-out war and nuclear war.

Kerry described the tension now as nowhere near what it was last April. He said the situation quieted down after that trip to China last April."The fact is, the United States and China agree on the fundamental importance of a denuclearized North Korea. There is no question of that," he said.

The top American diplomat, who is on his fifth trip to Asia in the past year, said China has a unique and critical role that it can play due to its economic, geographic, political and historical, cultural ties with North Korea. "No country has a greater potential to influence North Korea's behavior than China, given their extensive trading relationship with the North," he said, referring to the refined fuel, banking service and trade and assistance China provides to DPRK.

"So China has enormous ability to be able to have an impact here, and tomorrow my instructions from President Obama are to sit with the Chinese leadership and make the case that we cannot wait till the North has either gone so much further in its program that it's even more complicated to deal with," he said.

Kerry said China has done positive things but he said there is more that China can do. "But even as I say that, this is not just about what China does, this is about what all the Six-Party partners are prepared to do in order to try to move this issue once and for all," he said.

Some Chinese diplomats and analysts have questioned the extent to which the DPRK still listens to China, especially after the purge about two months ago of Chang Sung-taek, uncle of DPRK leader Kim Jong-un.

Kerry's remarks were made just a day after North and South Korean officials held their highest-level talks since 2007 on Wednesday in a bid to improve ties.

"We welcome the high-level talks between the DPRK and the ROK and wish the talks positive results," Chinese Foreign Ministry spokeswoman Hua Chunying said on Wednesday.

There are concerns that the DPRK might cancel the reunion plan to protest upcoming annual joint military drills by the US and South Korea. Pyongyang has demanded that Seoul postpone the drills. Kerry said on Thursday that the drills will be the same as those in previous years and the DPRK should not link them with the reunion.

"Given that the situation on the peninsula has eased recently, Kerry's visit will further improve the situation," said Wang Junsheng, a researcher on East Asian studies at the Chinese Academy of Social Sciences.

Shi Yongming, a researcher on Asia-Pacific studies at the China Institute of International Relations, said: "The DPRK has displayed a flexible approach in its foreign policy since the second half of last year. It has realized that it will not benefit from adopting a hard line toward the ROK and the US."

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